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At least 1,315 records · Page 73Linked to original sources

USGS2026

Fish introductions related to strong and diversifying effects on zooplankton assemblages in high-elevation mountain lakes

Freshwater environments are threatened by multiple anthropogenic stressors. High-elevation mountain lakes are particularly vulnerable to introduced nonnative fish and nutrient deposition because they were historically fishless and typically oligotrophic. To understand the potential effects of fish introduction and nutrient levels on high-elevation lake ecosystems, we assessed differences in zooplankton size, biomass, and density in 76 alpine and subalpine lakes in the Wind River Range, Wyoming, USA, and related those differences to the presence of introduced trout and to food quality (seston nutrient content) and quantity (chlorophyll a concentration). Trout presence, and to a lesser extent trout species, were the strongest predictors of zooplankton composition. Fishless lakes were dominated by low densities of copepods and other large-bodied taxa, and lakes with introduced trout were dominated by high densities of cladocerans, rotifers, and other small-bodied taxa. These assemblage differences are likely because trout reduce or eliminate all large zooplankton taxa by size-selective predation, including predation on Hesperodiaptomus shoshone (S. A. Forbes, 1893), a keystone species that effectively controls populations of rotifers and small crustacean zooplankton taxa. In contrast, the quantity and quality of seston was not associated with zooplankton assemblages. Zooplankton composition in lakes with Rocky Mountain Cutthroat Trout Oncorhynchus virginalis (Girard, 1856) or Golden Trout Oncorhynchus aguabonita (Jordan, 1892) was highly variable, but in lakes with primarily Brook Trout Salvelinus fontinalis (Mitchill, 1814), zooplankton composition was consistently distinct from that in fishless lakes, suggesting that Brook Trout introductions altered the zooplankton assemblage to a greater extent than Cutthroat or Golden trout did. These results contribute to global evidence that predatory fish introductions fundamentally restructure alpine lake food webs. The slow or incomplete recovery of native zooplankton assemblages following fish removal suggests long-term ecological legacies of fish introductions and highlights the importance of understanding factors that promote resilience in high-elevation lake ecosystems.

Wyoming↗

USGS1984

Age-related mortality in a wintering population of Dunlin

Despite considerable evidence that juvenile shorebirds experience significantly higher annual mortality rates than adults, identification and quantification of the sources of mortality have received little attention. We found that the proportion of juvenile Dunlins ( Calidris alpina ) in the kills of a Merlin ( Falco columbarius ) one winter at Bolinas Lagoon, California was greater than the proportion of juveniles in the lagoon's winter population. This is evidence that raptor predation may be one of the factors contributing to the age differences in annual mortality rates of shorebirds. We suggest that the greater vulnerability of juveniles to predation by the Merlin may be caused by age-related differences in Dunlin flocking behavior.

California↗

USGS1984

Observer visitation frequency and success of mourning dove nests: A field experiment

Field studies of nesting success generally require visits by the investigator to the nests under study. Such visits may themselves influence nesting success, however, and this possibility has been discussed and investigated by a number of workers with a variety of bird species. Livezey (1980) reviewed the relevant literature for duck nests and noted that most studies failed to demonstrate differences in nesting success between visited nests and those not visited. Livezey (1980) found in his own work that nest abandonment may have occurred as a result of disturbance by observers but that nest predation was not related to time spent by observers at nests or number of observers approaching nests. Various components of nesting and breeding success in seabirds are thought to be adversely affected by human disturbance and nest visitation (Gillett et al. 1975, Robert and Ralph 1975, Ollason and Dunnet 1980). Upland, ground-nesting species have also been studied (e.g. Stoddard 1931, Evans and Wolfe 1967, Henry 1969, Roseberry and Klimstra 1970, Klimstra and Roseberry 1975), and, although conclusions have varied, a number of these workers found no effect of observers on nest-predation rates.

The Auk↗

USGS2011

Nonlinear effects of group size on the success of wolves hunting elk

Despite the popular view that social predators live in groups because group hunting facilitates prey capture, the apparent tendency for hunting success to peak at small group sizes suggests that the formation of large groups is unrelated to prey capture. Few empirical studies, however, have tested for nonlinear relationships between hunting success and group size, and none have demonstrated why success trails off after peaking. Here, we use a unique dataset of observations of individually known wolves ( Canis lupus ) hunting elk ( Cervus elaphus ) in Yellowstone National Park to show that the relationship between success and group size is indeed nonlinear and that individuals withholding effort (free riding) is why success does not increase across large group sizes. Beyond 4 wolves, hunting success leveled off, and individual performance (a measure of effort) decreased for reasons unrelated to interference from inept hunters, individual age, or size. But performance did drop faster among wolves with an incentive to hold back, i.e., nonbreeders with no dependent offspring, those performing dangerous predatory tasks, i.e., grabbing and restraining prey, and those in groups of proficient hunters. These results suggest that decreasing performance was free riding and that was why success leveled off in groups with >4 wolves that had superficially appeared to be cooperating. This is the first direct evidence that nonlinear trends in group hunting success reflect a switch from cooperation to free riding. It also highlights how hunting success per se is unlikely to promote formation and maintenance of large groups.

Behavioral Ecology↗

USGS2004

Colonization, population growth, and nesting success of Black Oystercatchers following a seismic uplift

We present data on the colonization of Middleton Island, Alaska, by Black Oystercatchers ( Haematopus bachmani ) following the creation of an extensive rocky intertidal zone after the Alaskan earthquake of 1964. The first pair of oystercatchers was detected in 1976, and it was another 5 years before the population increased to three pairs. Oystercatcher numbers increased steadily thereafter, with a population explosion occurring in the 1990s. By 2002, there were 171 territorial pairs on the island. The total number of birds increased from two in 1976 to 718 in 2002. Breeding-pair densities on Middleton Island are the highest recorded for any portion of Alaska, averaging more than 5 pairs per km of shoreline in 2002. Nesting success in 2001 and 2002 was greater (83% or more of the eggs laid hatched) than that reported for any other population of oystercatchers in Alaska or along the Pacific Coast. We attribute this exponential growth rate and exceptionally high reproductive success to the large area of available and suitable habitat, the low number of avian predators and the complete lack of mammalian predators, low rate of nest loss to high tides and storm surges, and a low level of human disturbance. We propose nominating Middleton Island as a regional Western Hemisphere Shorebird Reserve Network site because a high percentage of the world's and region's population of Black Oystercatchers resides there during the breeding season. Further, since Middleton Island may be the single most important site in Alaska for Black Oystercatchers, we suggest it be protected from future development.

Alaska↗

USGS2005

Survival of captive-reared Puerto Rican Parrots released in the Caribbean National Forest

We report first-year survival for 34 captive-reared Puerto Rican Parrots ( Amazona vittata ) released in the Caribbean National Forest, Puerto Rico between 2000 and 2002. The purpose of the releases were to increase population size and the potential number of breeding individuals of the sole extant wild population, and to refine release protocols for eventual reintroduction of a second wild population elsewhere on the island. After extensive prerelease training, we released 10 parrots in 2000, 16 parrots in 2001, and eight parrots in 2002 ranging in age from 1–4 years old. All birds were equipped with radio-transmitters to monitor survival. The overall first-year survival estimate for the 34 parrots was 41% (CI = 22%–61%). Only one parrot died within the first week postrelease, with most (94%) surviving for at least eight weeks after release. Most (54%) documented mortalities were due to raptor predation, which claimed 21% of all released parrots. A captive-reared bird (male, age one), released in 2001, paired with a wild female and fledged two young in 2004. We also calculated survival based on 0% and 50% of observed predation losses and found hypothetical survival rates of 72% and 54%, respectively. Rigorous prerelease training and acclimation was believed to have improved initial postrelease parrot survival, and releasing mixed age-class groups suggests the potential for shortening the time to recruitment.

Puerto Rico↗

USGS1969

The fossil record of shell boring by snails

The predatory boring habit common to many recent snails probably arose first in the Polinicinae (Naticacea) during Upper Cretaceous (Cenomanian) times (100 million years B.P.) . In the fossil record the frequency of bored shells increases greatly in rocks of latest Cretaceous age and becomes more widespread during early Tertiary times coincident with the major diversification of the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show the same characteristics of preference of penetration in one pelecypod valve rather than the other or in position of the boring site on the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 million years old) that have previously been attributed to gastropod predation are herein attributed to other but unknown boring organisms. In part these borings are not accepted as evidence of Paleozoic gastropod predation because it necessitates: (1) Postulation of the separate development of a boring habit with its concomitant development of an accessory boring organ in a group whose descendants are all herbivores, and (2) The development of such a habit hundreds of millions of years before the appearance of any relatives of present day borers.

American Zoologist↗

USGS2024

Prey selection by black-footed ferrets (Mustela nigripes): Implications for intersexual resource partitioning and conservation

Intraspecific resource partitioning may play a critical role in how predators optimize prey selection. The Black-footed Ferret ( Mustela nigripes ; henceforth, ferret) is a highly specialized predator of prairie dogs ( Cynomys spp.; henceforth, PDs). Adult ferrets are sexually dimorphic and PDs are of similar size making them a difficult prey item. PD young are born 6 to 8 weeks prior to births of ferrets, producing a crop of smaller prey items during a period when energetic needs of female ferrets are highest. We asked whether relatively small female ferrets select small PDs as prey. We examined survival rates from early to late summer for large and small black-tailed PDs ( Cynomys ludovicianus ) in Montana and South Dakota as a function of their distance to adult male and female ferrets using capture–mark–recapture of PDs and simultaneous summer monitoring of ferret locations. Survival of small PDs (<600 g) was low when a female ferret was nearby, but distance to nearest female ferret did not affect survival of large PDs. Distance to the nearest male ferret did not influence survival regardless of PD size. Reduced competition from males for a critical food resource needed by females rearing young would benefit fitness of both sexes. If female ferrets depend on young PDs during their reproductive period, existing habitat models may substantially overestimate ferret carrying capacity.

Journal of Mammalogy↗

USGS1999

Preliminary survey for entomopathogenic fungi associated with Ixodes scapularis (Acari: Ixodidae) in southern New York and New England, USA

Free-living larval, nymphal, and adult Ixodes scapularis Say were collected from scattered locales in southern New England and New York to determine infection rates with entomopathogenic fungi. Infection rates of larvae, nymphs, males, and females were 0% (571), 0% (272), 0% (57), and 4.3% (47), respectively. Two entomopathogenic fungi were isolated from field-collected I. scapularis females from Fire Island, NY. Isolates were identified as Verticillium lecanii (Zimmermann) Viegas and Verticillium sp. (a member of the Verticillium lecanii species complex). Ixodes scapularis Say is the principal vector of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner ( Burgdorfer et al. 1982 , Johnson et al. 1984 ), the etiologic agent of Lyme disease in the northeastern and upper-midwestern United States. Control of I. scapularis is based on chemical treatment ( Mather et al. 1987b ; Schulze et al. 1987 , 1991 ), environmental management ( Wilson et al. 1988 , Schulze et al. 1995 ), and habitat modification ( Wilson 1986 ). These methods have shown variable success, and some potentially have negative environmental effects ( Wilson and Deblinger 1993 , Ginsberg 1994 ). Studies concerning natural predators, parasitoids, and pathogens of I. scapularis are rare. The use of ground-dwelling birds as tick predators has had only limited success ( Duffy et al. 1992 ). Nymphal I. scapularis are often infected with the parasitic wasp Ixodiphagus hookeri (Howard) ( Mather et al. 1987a , Hu et al. 1993 , Stafford et al. 1996 , Hu and Hyland 1997 ), but this wasp does not effectively control I. scapularis populations ( Stafford et al. 1996 ). The entomopathogenic nematodes Steinernema carpocapsae (Weiser) and S. glaseri (Steiner) are pathogenic only to engorged female I. scapularis, and thus have limited applicability ( Zhioua et al. 1995 ). In contrast, the entomogenous fungus Metarhizium anisopliae (Metschnikoff) Sorokin is highly pathogenic to all stages of I. scapularis, unfed as well as engorged, and thus has considerable potential as a microbial control agent ( Zhioua et al. 1997 ). European studies have suggested that entomopathogenic fungi might serve as natural controls of of Ixodes ricinus L. populations ( Samsinakova et al. 1974 , Eilenberg et al. 1991 , Kalsbeek et al. 1995 ). In the current study, we describe the isolation of entomopathogenic fungi from field-collected I. scapularis.

Journal of Medical Entomology↗

USGS2021

Golden Eagle dietary shifts following wildfire and shrub loss have negative consequences for nestling survivorship

Wildfires and invasive species have caused widespread changes in western North America’s shrub-steppe landscapes. The bottom–up consequences of degraded shrublands on predator ecology and demography remain poorly understood. We used a before–after paired design to study whether Golden Eagle ( Aquila chrysaetos ) diet and nestling survivorship changed following wildfires in southwestern Idaho, USA. We assessed burn extents from 1981 to 2013 and vegetation changes between 1979 (pre-burn) and 2014 (post-burn) within 3 km of Golden Eagle nesting centroids. We measured the frequency and biomass of individual prey, calculated diet diversity indexes, and monitored nestling survivorship at 15 territories in 1971–1981 and 2014–2015. On average, 0.70 of the area within 3 km of nesting centroids burned between 1981 and 2013, and the mean proportion of unburned shrubland decreased from 0.73 in 1979 to 0.22 in 2014. Diets in post-burn years were more diverse and had a lower proportion of some shrub-associated species, such as black-tailed jackrabbits ( Lepus californicus ) and mountain cottontails ( Sylvilagus nuttallii ), and a higher proportion of American Coots ( Fulica americana ), Mallards ( Anas platyrhynchos ), Piute ground squirrels ( Urocitellus mollis ), and Rock Pigeons ( Columba livia ) compared with pre-burn years. A high proportion of waterfowl represented a novel change in Golden Eagle diets, which are typically dominated by mammalian prey. Nestling survivorship was positively associated with the proportion of black-tailed jackrabbits and negatively associated with the proportion of Rock Pigeons in eagle diets. Rock Pigeons are a vector for Trichomonas gallinae , a disease-causing protozoan lethal to young eagles. Nesting attempts were more likely to fail (all young die) in the post-burn period compared with the pre-burn period. Dietary shifts are a common mechanism for predators to cope with landscape change, but shifts away from preferred prey to disease vectors affect nestling survivorship and could lead to population-level effects on productivity.

Idaho↗

USGS2023

Nest traits and major flooding events influence nest survival of Emperor Geese while regional environmental variation linked to climate does not

The reproductive ecology of geese that breed in the Arctic and subarctic is likely susceptible to the effects of climate change, which is projected to alter the environmental conditions of northern latitudes. Nest survival is an important component of productivity in geese; however, the effects of regional environmental conditions on nest survival are not well understood for some species, including the Emperor Goose ( Anser canagicus ), a species of conservation concern that is endemic to the Bering Sea region. We estimated nest survival and examined how indices of regional environmental conditions, nest traits (nest age, initiation date, and maximum number of eggs in the nest), and researcher disturbance influenced daily survival probability (DSP) of Emperor Goose nests using hierarchical models and 24 years of nest monitoring data (1994–2017) from the Yukon–Kuskokwim Delta (Y–K Delta) in western Alaska. Our results indicate that overall nest survival was generally high (µ = 0.766, 95% CRI: 0.655–0.849) and ranged from 0.327 (95% CRI: 0.176–0.482) in 2013 to 0.905 (95% CRI: 0.839–0.953) in 1995. We found that DSPs of nests were influenced by nest traits, negatively influenced by major tidal flooding events and by researcher disturbance, but were not influenced by regional indices of spring timing, temperature and precipitation during nesting, or fox and vole abundance on the Y–K Delta. However, the number of nests found each year was negatively related to our index of fox abundance, suggesting nests that failed as a result of fox predation may have never been discovered due to our limited nest-searching efforts during egg laying. Our results suggest that regional environmental variation had minimal influence on the nest survival of Emperor Geese, although major flooding events were important. Nevertheless, we suspect that within-year variation in local weather conditions and local abundance of predators and alternative prey may be important and should be considered in future studies.

Alaska↗

USGS2013

How to predict community responses to perturbations in the face of imperfect knowledge and network complexity

Recent attempts to predict the response of large food webs to perturbations have revealed that in larger systems increasingly precise information on the elements of the system is required. Thus, the effort needed for good predictions grows quickly with the system's complexity. Here, we show that not all elements need to be measured equally well, suggesting that a more efficient allocation of effort is possible. We develop an iterative technique for determining an efficient measurement strategy. In model food webs, we find that it is most important to precisely measure the mortality and predation rates of long-lived, generalist, top predators. Prioritizing the study of such species will make it easier to understand the response of complex food webs to perturbations.

Proceedings of the Royal Society B: Biological Sci↗

USGS2015

Marine foraging ecology influences mercury bioaccumulation in deep-diving northern elephant seals

Mercury contamination of oceans is prevalent worldwide and methylmercury concentrations in the mesopelagic zone (200–1000 m) are increasing more rapidly than in surface waters. Yet mercury bioaccumulation in mesopelagic predators has been understudied. Northern elephant seals (Mirounga angustirostris) biannually travel thousands of kilometres to forage within coastal and open-ocean regions of the northeast Pacific Ocean. We coupled satellite telemetry, diving behaviour and stable isotopes (carbon and nitrogen) from 77 adult females, and showed that variability among individuals in foraging location, diving depth and δ 13 C values were correlated with mercury concentrations in blood and muscle. We identified three clusters of foraging strategies, and these resulted in substantially different mercury concentrations: (i) deeper-diving and offshore-foraging seals had the greatest mercury concentrations, (ii) shallower-diving and offshore-foraging seals had intermediate levels, and (iii) coastal and more northerly foraging seals had the lowest mercury concentrations. Additionally, mercury concentrations were lower at the end of the seven-month-long foraging trip (n = 31) than after the two-month- long post-breeding trip (n = 46). Our results indicate that foraging behaviour influences mercury exposure and mesopelagic predators foraging in the northeast Pacific Ocean may be at high risk for mercury bioaccumulation.

California↗

USGS2024

Ungulate personality and the human shield contribute to long-distance migration loss

Long-distance ungulate migrations are declining and past research has focused on preserving migration paths where habitat fragmentation and loss disrupts movement corridors. However, changing residency-migration tradeoffs are the stronger driver of long-distance migration loss in some populations. The human shield effect relative to predation risk and anthropogenic food resources likely shapes these tradeoffs, but individual animals also vary in their propensity to tolerate proximity to humans and developed areas. We investigated how personality relative to human-habituation affects migration behavior. We categorized elk as bold or shy based on use of anthropogenic food resources identified through a clustering algorithm applied to GPS collar data. Bold elk were 4 times more likely to select wintering areas close to human activity and migrated 60% shorter distances compared to shy elk. As a result, elk wintering grounds were spatially structured such that conflict- and disease-prone individuals selected areas adjacent to human activity. Our results suggest that bold personality traits act as a precursor to human-habituation, which permits bold elk to reap the forage and predation rewards that occur in suburban landscapes. A multi-pronged approach beyond just maintaining habitat corridors may be necessary to conserve long-distance migrations for species that can become human-habituated.

BioRxiv↗

USGS2025

A systematic literature review of forecasting and predictive models of harmful algal blooms in flowing waters

Occurrences of harmful algal blooms (HABs) in rivers challenge the belief that rivers are not susceptible to HABs because of their short residence times and fluctuating hydrology. Here we present a systematic literature review of predictive and forecasting models for HABs in flowing waters, including rivers, flowing in-stream reservoirs (e.g., run-of-river reservoirs and lock-and-dam systems) and tidal or estuarine systems with riverine processes. The review aimed to understand current and historical modeling approaches for predicting and forecasting river HABs, without restricting to specific taxa, such as cyanobacteria, or modeling endpoints. The review included 162 articles published over nearly 50 years, covering more than 80 rivers worldwide. Eutrophic, non-wadable rivers with in-stream obstruction were commonly modeled, though diverse environmental characteristics were reported. Most articles used algal biomass or chlorophyll as modeling endpoints, with a quarter using novel or unique endpoints. Algal toxins motivated model development in 23% of the articles, however just 5% used algal toxins as an endpoint. Only 6% of the articles modeled benthic HABs; the rest focused on pelagic HABs. There was no standard model used for modeling river HABs. Process-based models were more common (59%) than data-driven approaches (37%), with model formulations ranging from simple to complex, which contrasts with a lake-focused literature review of HAB models that found data-driven models were more common. Models in river settings shared similar input variables as those previously identified for lakes, such as water temperature, nutrients, and light availability. However, streamflow and other transport metrics took prominence in river models compared to lake models. Algal cell physiology (such as growth, predation, and motility) was routinely included as input data or as mathematical formulations in process-based models and these processes were frequently identified as an important predictor by the articles’ authors. Conversely, data-driven models rarely included these processes, instead using predictors related to environmental conditions, such as nutrients, water quality, water temperature, and streamflow. These important proxy predictors have apparent success with modeling overall algal biomass (irrespective of taxa) whereas other factors, such as those related to algal physiology and other biological processes, are likely responsible for more subtle shifts in community composition. These differences highlight the influence of data availability, especially for processes that are difficult, time-consuming, or expensive to measure, on model development and model outcomes, raising questions about the selection of modeling inputs and endpoints. Challenges to advancing river HAB modeling include the lack of site-specific model inputs representing key processes (e.g., photosynthetic parameters and predation rates), overlooked riverine environments like the benthos and side/back-channel areas, lack of information on environmental settings, and poorly reported model performance metrics. This review emphasizes opportunities for advancing river HAB modeling by learning from well-honed estuarine models, supporting current forecasting and operationalization efforts, and developing common datasets for river HAB model development and evaluation.

BioRxiv↗

USGS2019

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

A central theme of range‐limit theory (RLT) posits that abiotic factors form high‐latitude/altitude limits, whereas biotic interactions create lower limits. This hypothesis, often credited to Charles Darwin, is a pattern widely assumed to occur in nature. However, abiotic factors can impose constraints on both limits and there is scant evidence to support the latter prediction. Deviations from these predictions may arise from correlations between abiotic factors and biotic interactions, as a lack of data to evaluate the hypothesis, or be an artifact of scale. Combining two tenets of ecology—niche theory and predator–prey theory—provides an opportunity to understand how biotic interactions influence range limits and how this varies by trophic level. We propose an expansion of RLT, interactive RLT (iRLT), to understand the causes of range limits and predict range shifts. Incorporating the main predictions of Darwin's hypothesis, iRLT hypothesizes that abiotic and biotic factors can interact to impact both limits of a species’ range. We summarize current thinking on range limits and perform an integrative review to evaluate support for iRLT and trophic differences along range margins, surveying the mammal community along the boreal‐temperate and forest‐tundra ecotones of North America. Our review suggests that range‐limit dynamics are more nuanced and interactive than classically predicted by RLT. Many (57 of 70) studies indicate that biotic factors can ameliorate harsh climatic conditions along high‐latitude/altitude limits. Conversely, abiotic factors can also mediate biotic interactions along low‐latitude/altitude limits (44 of 68 studies). Both scenarios facilitate range expansion, contraction or stability depending on the strength and the direction of the abiotic or biotic factors. As predicted, biotic interactions most often occurred along lower limits, yet there were trophic differences. Carnivores were only limited by competitive interactions ( n = 25), whereas herbivores were more influenced by predation and parasitism (77%; 55 of 71 studies). We highlight how these differences may create divergent range patterns along lower limits. We conclude by (a) summarizing iRLT; (b) contrasting how our model system and others fit this hypothesis and (c) suggesting future directions for evaluating iRLT.

Journal of Animal Ecology↗

USGS2012

Invasive species management restores a plant-pollinator mutualism in Hawaii

1.The management and removal of invasive species may give rise to unanticipated changes in plant–pollinator mutualisms because they can alter the composition and functioning of plant–pollinator interactions in a variety of ways. To utilize a functional approach for invasive species management, we examined the restoration of plant–pollinator mutualisms following the large-scale removal of an invasive nectar thief and arthropod predator, Vespula pensylvanica. 2.We reduced V. pensylvanica populations in large plots managed over multiple years to examine the response of plant–pollinator mutualisms and the fruit production of a functionally important endemic Hawaiian tree species, Metrosideros polymorpha. To integrate knowledge of the invader's behaviour and the plant's mating system, we determined the efficacy of V. pensylvanica as a pollinator of M. polymorpha and quantified the dependence of M. polymorpha on animal pollination (e.g. level of self-compatibility and pollen limitation). 3.The reduction of V. pensylvanica in managed sites, when compared to unmanaged sites, resulted in a significant increase in the visitation rates of effective bee pollinators (e.g. introduced Apis mellifera and native Hylaeus spp.) and in the fruit production of M. polymorpha. 4.Apis mellifera, following the management of V. pensylvanica, appears to be acting as a substitute pollinator for M. polymorpha, replacing extinct or threatened bird and bee species in our study system. 5.Synthesis and applications. Fruit production of the native M. polymorpha was increased after management of the invasive pollinator predator V. pensylvanica; however, the main pollinators were no longer native but introduced. This research thus demonstrates the diverse impacts of introduced species on ecological function and the ambiguous role they play in restoration. We recommend incorporating ecological function and context into invasive species management as this approach may enable conservation managers to simultaneously minimize the negative and maximize the positive impacts (e.g. taxon substitution) of introduced species. Such novel restoration approaches are needed, especially in highly degraded ecosystems.

Hawai'i↗

USGS2013

Relative influence of human harvest, carnivores, and weather on adult female elk survival across western North America

Well-informed management of harvested species requires understanding how changing ecological conditions affect demography and population dynamics, information that is lacking for many species. We have limited understanding of the relative influence of carnivores, harvest, weather and forage availability on elk Cervus elaphus demography, despite the ecological and economic importance of this species. We assessed adult female survival, a key vital rate for population dynamics, from 2746 radio-collared elk in 45 populations across western North America that experience wide variation in carnivore assemblage, harvest, weather and habitat conditions. Proportional hazard analysis revealed that 'baseline' (i.e. not related to human factors) mortality was higher with very high winter precipitation, particularly in populations sympatric with wolves Canis lupus. Mortality may increase via nutritional stress and heightened vulnerability to predation in snowy winters. Baseline mortality was unrelated to puma Puma concolor presence, forest cover or summer forage productivity. Cause-specific mortality analyses showed that wolves and all carnivore species combined had additive effects on baseline elk mortality, but only reduced survival by <2%. When human factors were included, ‘total’ adult mortality was solely related to harvest; the influence of native carnivores was compensatory. Annual total mortality rates were lowest in populations sympatric with both pumas and wolves because managers reduced female harvest in areas with abundant or diverse carnivores. Mortality from native carnivores peaked in late winter and early spring, while harvest-induced mortality peaked in autumn. The strong peak in harvest-induced mortality during the autumn hunting season decreased as the number of native carnivore species increased. Synthesis and applications. Elevated baseline adult female elk mortality from wolves in years with high winter precipitation could affect elk abundance as winters across the western US become drier and wolves recolonize portions of the region. In the absence of human harvest, wolves had additive, although limited, effects on mortality. However, human harvest, and its apparent use by managers to offset predation, primarily controls overall variation in adult female mortality. Altering harvest quotas is thus a strong tool for offsetting impacts of carnivore recolonization and shifting weather patterns on elk across western North America.

Colorado;Idaho;Montana;Utah;Washington;Wyoming↗